With the coming of blood component therapy, most whole blood collected today is separated into its clinically proven components for storage and administration. The clinically proven components of whole blood include red blood cells, used to treat chronic anemia; platelet-poor plasma, from which Clotting Factor VIII-rich cryoprecipitate can be obtained for the treatment of hemophilia; and concentrations of platelets, used to control thrombocytopenic bleeding.
It is well known that blood can carry infectious agents like hepatitis-B virus; the human immunodeficiency (AIDS) virus; the Herpes virus; and the influenza virus. To avoid the transmission of these infectious agents during blood transfusions, donors of blood are routinely screened and also undergo serologic testing to detect the presence of these agents. Still, it is difficult to always assure that these infectious agents are detected.
The use of photodynamic therapy has been suggested as a way to eradicate infectious agents from collected blood and its components. See Matthews et al, "Photodynamic Therapy of Viral Contaminants With Potential for Blood Bank Applications," Transfusion, 28(1), pp. 81-83 (1988). Various extracorporeal systems have been proposed that use photodynamic therapy to treat blood prior to storage and transfusion. See, for example, Edelson U.S. Pat. Nos. 4,613,322 and 4,684,521; Troutner et al U.S. Pat. No. 4,708,715; Wiesehahn et al U.S. Pat. No. 4,727,027; Sieber U.S. Pat. Nos. 4,775,625 and 4,915,683; and Judy et al U.S. Pat. No. 4,878,891.
To date, there has been a general lack of success in economically adapting the benefits of photodynamic therapy to the demands of the blood banking industry. One reason for this is that not all biological contaminants are carried free within the blood where they can be readily coupled to photoactive agents. Some biological contaminants are entrained on or within white blood cells out of the reach of photoactive agents.
The extracorporeal systems proposed to date can eradicate only contaminants that are carried free within the blood. Prior systems have not provided a device that can remove both free and entrained biological contaminants from a fluid in a single pass through a single treatment zone.
For this and other reasons, the promise of photodynamic therapy in treating the nation's banked blood supply has gone largely unfulfilled.